Add basic macOS support

Examples/PreviewSnapshotsTestAppTests/PreviewSnapshotsTestAppTests.swift

@@ -20,26 +20,32 @@ import XCTest
 
 final class PreviewSnapshotsTestAppTests: XCTestCase {
     func test_simpleViewSnapshots() {
-        SimpleView_Previews.snapshots.assertSnapshots(as: .testStrategy())
+        SimpleView_Previews.snapshots.assertSnapshots(as: .testStrategy(), named: platformName)
     }
 
     func test_previewStateViewSnapshots() {
-        PreviewStateView_Previews.snapshots.assertSnapshots(as: .testStrategy())
+        PreviewStateView_Previews.snapshots.assertSnapshots(as: .testStrategy(), named: platformName)
     }
 
     func test_observableObjectSnapshots() {
-        ObservableObjectView_Previews.snapshots.assertSnapshots(as: .testStrategy())
+        ObservableObjectView_Previews.snapshots.assertSnapshots(as: .testStrategy(), named: platformName)
     }
 
     func test_previewStateLightAndDark() {
         PreviewStateView_Previews.snapshots
-            .assertSnapshots(as: [
-                "Light": .testStrategy(userInterfaceStyle: .light),
-                "Dark": .testStrategy(userInterfaceStyle: .dark),
-            ])
+            .assertSnapshots(
+                as: [
+                    "Light": .testStrategy(userInterfaceStyle: .light),
+                    "Dark": .testStrategy(userInterfaceStyle: .dark),
+                ],
+                named: platformName
+            )
     }
 }
 
+#if os(iOS)
+let platformName = "iOS"
+
 extension Snapshotting where Value: SwiftUI.View, Format == UIImage {
     /// Shared image test strategy
     static func testStrategy(userInterfaceStyle: UIUserInterfaceStyle = .light) -> Self {
@@ -54,3 +60,48 @@ extension Snapshotting where Value: SwiftUI.View, Format == UIImage {
         )
     }
 }
+#elseif os(macOS)
+let platformName = "macOS"
+
+extension Snapshotting where Value: SwiftUI.View, Format == NSImage {
+    /// Shared image test strategy
+    static func testStrategy(userInterfaceStyle: UserInterfaceStyle = .light) -> Self {
+        let snapshotting = Snapshotting<NSView, NSImage>.image(size: .init(width: 400, height: 400)).pullback { (view: Value) in
+            let view = NSHostingView(rootView: view.environment(\.colorScheme, userInterfaceStyle.colorScheme))
+            view.wantsLayer = true
+            view.layer?.backgroundColor = NSColor.windowBackgroundColor.cgColor
+            return view
+        }
+
+        return Snapshotting(
+            pathExtension: snapshotting.pathExtension,
+            diffing: snapshotting.diffing,
+            asyncSnapshot: { view in
+                Async { callback in
+                    userInterfaceStyle.appearance.performAsCurrentDrawingAppearance {
+                        snapshotting.snapshot(view).run(callback)
+                    }
+                }
+            }
+        )
+    }
+}
+
+enum UserInterfaceStyle {
+    case light, dark
+
+    var colorScheme: ColorScheme {
+        switch self {
+        case .light: return .light
+        case .dark: return .dark
+        }
+    }
+
+    var appearance: NSAppearance {
+        switch self {
+        case .light: return NSAppearance(named: .aqua)!
+        case .dark: return NSAppearance(named: .darkAqua)!
+        }
+    }
+}
+#endif

Package.swift

@@ -7,6 +7,7 @@ let package = Package(
     platforms: [
         .iOS(.v13),
         .tvOS(.v13),
+        .macOS(.v10_15),
     ],
     products: [
         .library(

Sources/PreviewSnapshotsTesting/PreviewSnapshots+assertSnapshots.swift

@@ -20,7 +20,7 @@ extension PreviewSnapshots {
     /// snapshots recorded on disk.
     ///
     /// - Parameters:
-    ///   - snapshotting: Snapshotting instance for  `AnyView` into a `UIImage`.
+    ///   - snapshotting: Strategy for serializing, deserializing, and comparing `AnyView`.
     ///   - name: An optional description of the snapshot to include with the configuration name.
     ///   - recording: Whether or not to record a new reference.
     ///   - file: The file in which failure occurred. Defaults to the file name of the test case in
@@ -29,8 +29,8 @@ extension PreviewSnapshots {
     ///         of the test case in which this function was called.
     ///   - line: The line number on which failure occurred. Defaults to the line number on which
     ///         this function was called.
-    public func assertSnapshots(
-        as snapshotting: Snapshotting<AnyView, UIImage> = .image,
+    public func assertSnapshots<Format>(
+        as snapshotting: Snapshotting<AnyView, Format>,
         named name: String? = nil,
         record recording: Bool = false,
         file: StaticString = #file,
@@ -62,8 +62,8 @@ extension PreviewSnapshots {
     ///         of the test case in which this function was called.
     ///   - line: The line number on which failure occurred. Defaults to the line number on which
     ///         this function was called.
-    public func assertSnapshots(
-        as strategies: [String: Snapshotting<AnyView, UIImage>],
+    public func assertSnapshots<Format>(
+        as strategies: [String: Snapshotting<AnyView, Format>],
         named name: String? = nil,
         record recording: Bool = false,
         file: StaticString = #file,
@@ -96,8 +96,8 @@ extension PreviewSnapshots {
     ///         of the test case in which this function was called.
     ///   - line: The line number on which failure occurred. Defaults to the line number on which
     ///         this function was called.
-    public func assertSnapshots(
-        as strategies: [Snapshotting<AnyView, UIImage>],
+    public func assertSnapshots<Format>(
+        as strategies: [Snapshotting<AnyView, Format>],
         named name: String? = nil,
         record recording: Bool = false,
         file: StaticString = #file,
@@ -131,14 +131,14 @@ extension PreviewSnapshots {
     ///
     /// ```swift
     /// func test_snapshots() {
-    ///     ContentView_Previews.snapshots.assertSnapshots {
+    ///     ContentView_Previews.snapshots.assertSnapshots(as: .image) {
     ///         $0.border(.red)
     ///     }
     /// }
     /// ```
     ///
     /// - Parameters:
-    ///   - snapshotting: Snapshotting instance that converts an `AnyView` into a `UIImage`.
+    ///   - snapshotting: Strategy for serializing, deserializing, and comparing `AnyView`.
     ///   - name: An optional description of the snapshot to include with the configuration name.
     ///   - recording: Whether or not to record a new reference.
     ///   - file: The file in which failure occurred. Defaults to the file name of the test case in
@@ -148,8 +148,8 @@ extension PreviewSnapshots {
     ///   - line: The line number on which failure occurred. Defaults to the line number on which
     ///         this function was called.
     ///   - modify: A closure to update the preview content before snapshotting.
-    public func assertSnapshots<Modified: View>(
-        as snapshotting: Snapshotting<Modified, UIImage> = .image,
+    public func assertSnapshots<Modified: View, Format>(
+        as snapshotting: Snapshotting<Modified, Format>,
         named name: String? = nil,
         record recording: Bool = false,
         file: StaticString = #file,
@@ -178,7 +178,10 @@ extension PreviewSnapshots {
     ///
     /// ```swift
     /// func test_snapshots() {
-    ///     ContentView_Previews.snapshots.assertSnapshots {
+    ///     ContentView_Previews.snapshots.assertSnapshots(as: [
+    ///         "Light": .image(traits: UITraitCollection(userInterfaceStyle: .light)),
+    ///         "Dark": .image(traits: UITraitCollection(userInterfaceStyle: .dark)),
+    ///     ] {
     ///         $0.border(.red)
     ///     }
     /// }
@@ -196,8 +199,8 @@ extension PreviewSnapshots {
     ///   - line: The line number on which failure occurred. Defaults to the line number on which
     ///         this function was called.
     ///   - modify: A closure to update the preview content before snapshotting.
-    public func assertSnapshots<Modified: View>(
-        as strategies: [String: Snapshotting<AnyView, UIImage>],
+    public func assertSnapshots<Modified: View, Format>(
+        as strategies: [String: Snapshotting<AnyView, Format>],
         named name: String? = nil,
         record recording: Bool = false,
         file: StaticString = #file,
@@ -228,7 +231,10 @@ extension PreviewSnapshots {
     ///
     /// ```swift
     /// func test_snapshots() {
-    ///     ContentView_Previews.snapshots.assertSnapshots {
+    ///     ContentView_Previews.snapshots.assertSnapshots(as: [
+    ///         .image(layout: .fixed(width: 200, height: 200),
+    ///         .image(layout: .fixed(width: 400, height: 400),
+    ///     ]) {
     ///         $0.border(.red)
     ///     }
     /// }
@@ -245,8 +251,8 @@ extension PreviewSnapshots {
     ///   - line: The line number on which failure occurred. Defaults to the line number on which
     ///         this function was called.
     ///   - modify: A closure to update the preview content before snapshotting.
-    public func assertSnapshots<Modified: View>(
-        as strategies: [Snapshotting<Modified, UIImage>],
+    public func assertSnapshots<Modified: View, Format>(
+        as strategies: [Snapshotting<Modified, Format>],
         named name: String? = nil,
         record recording: Bool = false,
         file: StaticString = #file,
@@ -268,6 +274,76 @@ extension PreviewSnapshots {
     }
 }
 
+#if os(iOS) || os(tvOS)
+// MARK: - UIImage defaults
+
+extension PreviewSnapshots {
+    /// Assert that all of the snapshots defined in a `PreviewSnapshots` collection match their
+    /// snapshots recorded on disk using the `Snapshotting<AnyView, UIImage>.image` strategy.
+    ///
+    /// - Parameters:
+    ///   - name: An optional description of the snapshot to include with the configuration name.
+    ///   - recording: Whether or not to record a new reference.
+    ///   - file: The file in which failure occurred. Defaults to the file name of the test case in
+    ///         which this function was called.
+    ///   - testName: The name of the test in which failure occurred. Defaults to the function name
+    ///         of the test case in which this function was called.
+    ///   - line: The line number on which failure occurred. Defaults to the line number on which
+    ///         this function was called.
+    public func assertSnapshots(
+        named name: String? = nil,
+        record recording: Bool = false,
+        file: StaticString = #file,
+        testName: String = #function,
+        line: UInt = #line
+    ) {
+        assertSnapshots(as: .image, named: name, record: recording, file: file, testName: testName, line: line)
+    }
+}
+
+// MARK: - PreviewSnapshots.assertSnapshots + modify
+
+extension PreviewSnapshots {
+    /// Assert that all of the snapshots defined in a `PreviewSnapshots` collection match their
+    /// snapshots recorded on disk using the `Snapshotting<AnyView, UIImage>.image` strategy after
+    /// applying some modification.
+    ///
+    /// `modify` can be used to update the configured view in a way that's useful for snapshotting,
+    /// but doesn't make sense for previews.
+    ///
+    /// For example, adding a border to better visualize the edges of the view in snapshots:
+    ///
+    /// ```swift
+    /// func test_snapshots() {
+    ///     ContentView_Previews.snapshots.assertSnapshots {
+    ///         $0.border(.red)
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// - Parameters:
+    ///   - name: An optional description of the snapshot to include with the configuration name.
+    ///   - recording: Whether or not to record a new reference.
+    ///   - file: The file in which failure occurred. Defaults to the file name of the test case in
+    ///         which this function was called.
+    ///   - testName: The name of the test in which failure occurred. Defaults to the function name
+    ///         of the test case in which this function was called.
+    ///   - line: The line number on which failure occurred. Defaults to the line number on which
+    ///         this function was called.
+    ///   - modify: A closure to update the preview content before snapshotting.
+    public func assertSnapshots<Modified: View>(
+        named name: String? = nil,
+        record recording: Bool = false,
+        file: StaticString = #file,
+        testName: String = #function,
+        line: UInt = #line,
+        modify: (AnyView) -> Modified
+    ) {
+        assertSnapshots(as: .image, named: name, record: recording, file: file, testName: testName, line: line, modify: modify)
+    }
+}
+#endif
+
 // MARK: Configuration name helper
 
 private extension PreviewSnapshots.Configuration {

Tests/PreviewSnapshotsTests/PreviewSnapshotsTests.swift

@@ -40,33 +40,7 @@ final class PreviewSnapshotsTests: XCTestCase {
             }
         )
 
-        snapshots.assertSnapshots(as: .testStrategy)
-    }
-
-    /// PreviewSnapshots assertion using `named` parameter
-    func test_namedAssertion() {
-        struct ContentView: View {
-            let message: String
-
-            var body: some View {
-                Text(message)
-                    .font(.largeTitle)
-                    .foregroundColor(.blue)
-                    .padding(8)
-            }
-        }
-
-        let snapshots = PreviewSnapshots<String>(
-            configurations: [
-                .init(name: "Short Message", state: "Hello!"),
-                .init(name: "Long Message", state: "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.")
-            ],
-            configure: { message in
-                ContentView(message: message)
-            }
-        )
-
-        snapshots.assertSnapshots(as: .testStrategy, named: "Named Assertion")
+        snapshots.assertSnapshots(as: .testStrategy, named: frameworkName)
     }
 
     /// PreviewSnapshots with a tuple as the state
@@ -105,7 +79,7 @@ final class PreviewSnapshotsTests: XCTestCase {
             }
         )
 
-        snapshots.assertSnapshots(as: .testStrategy)
+        snapshots.assertSnapshots(as: .testStrategy, named: frameworkName)
     }
 
     /// PreviewSnapshots with an ObservableObject as the state
@@ -144,7 +118,7 @@ final class PreviewSnapshotsTests: XCTestCase {
             }
         )
 
-        snapshots.assertSnapshots(as: .testStrategy)
+        snapshots.assertSnapshots(as: .testStrategy, named: frameworkName)
     }
 
     /// PreviewSnapshots using a NamedPreviewState as the state
@@ -193,7 +167,7 @@ final class PreviewSnapshotsTests: XCTestCase {
             }
         )
 
-        snapshots.assertSnapshots(as: .testStrategy)
+        snapshots.assertSnapshots(as: .testStrategy, named: frameworkName)
     }
 
     /// PreviewSnapshots using assertSnapshots's modify function
@@ -218,11 +192,13 @@ final class PreviewSnapshotsTests: XCTestCase {
             }
         )
 
-        snapshots.assertSnapshots(as: .testStrategy) { view in
+        snapshots.assertSnapshots(as: .testStrategy, named: frameworkName) { view in
             view.border(Color.blue)
         }
     }
 }
+#if os(iOS) || os(tvOS)
+let frameworkName = "UIKit"
 
 extension Snapshotting where Value: SwiftUI.View, Format == UIImage {
     /// Shared image test strategy
@@ -233,3 +209,18 @@ extension Snapshotting where Value: SwiftUI.View, Format == UIImage {
         )
     }
 }
+#elseif os(macOS)
+let frameworkName = "AppKit"
+
+extension Snapshotting where Value: SwiftUI.View, Format == NSImage {
+    /// Shared image test strategy
+    static var testStrategy: Self {
+        Snapshotting<NSView, NSImage>.image(size: .init(width: 400, height: 400)).pullback { view in
+            let view = NSHostingView(rootView: view)
+            view.wantsLayer = true
+            view.layer?.backgroundColor = NSColor.windowBackgroundColor.cgColor
+            return view
+        }
+    }
+}
+#endif